Fullerene-tetracyanoquinodimethane thin film and novel electrical bistability
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Fullerene-tetracyanoquinodimethane thin film and novel electrical bistability H. J. Gao,a) Z. Q. Xue, Q. D. Wu, and S. J. Pang Beijing Laboratory of Vacuum Physics, Chinese Academy of Sciences, P. O. Box 2724, Beijing 100080, and Department of Radio-Electronics, Peking University, Beijing 100871, China (Received 12 December 1994; accepted 29 July 1995)
We report the electrical bistability of C60 -tetracyanoquinodimethane (TCNQ) thin films fabricated by using an ionized-cluster-beam method in a high vacuum system. The films were characterized by transmission electron microscopy and electronic absorption spectroscopy. The spectroscopic results showed evidence of the formation of the charge-transfer complex system in C60 -TCNQ thin films, and the TEM results revealed the microstructure of the films. The film thickness is ,100 nm. The electromotive intensity at the transition point was of the order of 106 Vym. The possible mechanism of the electrical phenomena of the films is discussed in the paper.
Much more interest has been focused on the C60 and polymers in the application of electronic and optoelectric devices and even molecular electronics in recent years.1–4 Tetracyanoquinodimethane (TCNQ),5 when combined with some metals, may exhibit special properties such as electrical switching, which may be useful for applications in integrated devices. Melby and co-workers have exhibited the electrical switching and phototransformation phenomena of CuTCNQ and AgTCNQ.6,7 Potember and co-workers8 have reported the stable and reducible electric bistability of the copper and silver salts of organic electron acceptors such as TCNQ, tetracyanoethylene (TCNE), and tetracyanonapthoquinodimethane (TNAP). Gong et al.9 have also studied the bistable switching of CuTCNQ and LiTCNQ. However, the organic functional thin films mentioned above were generally deposited by the vacuum evaporation deposition method or the chemical deposition in solution. In this Communication, we report, for the first time to our knowledge, the electrical characteristics and the ionized-cluster-beam (ICB) deposition of C60 -TCNQ thin films. Since the ICB deposition10,11 is carried out in a high vacuum and is capable of controlling the structure of the deposited films according to the parameters of the ICB system, such as ionizing voltage and accelerating voltage as well as the substrate temperature, it is more powerful to fabricate desired films whose properties can be controlled where fewer impurities and defects exist.
a)
Author to whom all correspondence should be addressed. J. Mater. Res., Vol. 11, No. 4, Apr 1996
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In the past decades, many kinds of high quality inorganic materials have been successfully fabricated by using this deposition method,12–15 and now it is also a promising method for preparation of organic thin films.16–18 The highly pure TCNQ material was purchased from Sigma Chemical Corporation. The pure C60 and the mixture of C60yC70 (85
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